Methods and an associated system for processing unhardened concrete are disclosed. With these methods, the porosity of the unhardened concrete is significantly increased to decrease the strength so much that it can be easily broken up for sale or reuse. In at least one embodiment, the method includes adding a large volume of foam to the returned unhardened concrete and then mixing the foam with the returned concrete in the ready-mix concrete truck or other concrete mixing devices at any location including the jobsite, enroute to the concrete plant, or at the concrete plant. Through the mixing of foam with the returned concrete, the hydrated cement and aggregate particles are separated by large volumes of air voids, which significantly increase the porosity and dramatically reduce the strength of the returned concrete. The treated concrete is discharged and allowed to solidify in this weakened state, after which it is easily broken into loose particulate material that can be sold or reused.